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A daggerboard is a retractable centreboard used by various sailing craft. While other types of centreboard may pivot to retract, a daggerboard slides in a casing. The shape of the daggerboard converts the forward motion into a windward lift, countering the leeward push of the sail. The theoretical centre of lateral resistance is on the trailing ...
The ring constitutes the rotor of an electric motor and sits within a surrounding stator, which is also ring-shaped and creates the necessary torque. Rotor and stator are water tight and the whole unit operates submerged. Similar to an azipod, a rim-driven thruster can be designed to be fixed, retractable and/or azimuthing.
Kort nozzle The towboat Dolphin I in a floating drydock on the Mississippi River in Algiers, Louisiana.. A ducted propeller, also known as a Kort nozzle, is a marine propeller fitted with a non-rotating nozzle.
The air-filled rubber membrane uses the same principles as the nozzle system to reduce cavitation in marine propellers. As the nozzle system requires a large source of energy to operate, the creators sought to develop a lower cost system.
Finnish outdoor utility knife, puukko Retractable blade knife with replaceable utility blade A utility knife is any type of knife used for general manual work purposes. [1] Such knives were originally fixed-blade knives with durable cutting edges suitable for rough work such as cutting cordage, cutting/scraping hides, butchering animals, cleaning fish scales, reshaping timber, and other tasks.
English inventor Francis Ronalds described what he called a propelling rudder in 1859 that combined the propulsion and steering mechanisms of a boat in a single apparatus. . The propeller was placed in a frame having an outer profile similar to a rudder and attached to a vertical shaft that allowed the device to rotate in plane while spin was transmitted to the propell
A small boat stuffing box comprising an adjusting nut, a locking nut and a sleeve. On a boat having an inboard motor that turns a shaft attached to an external propeller, the shaft passes through a stuffing box, also called a "packing box" or "stern gland" in this application. The stuffing box prevents water from entering the boat's hull.
In 1802, American lawyer and inventor John Stevens built a 25-foot (7.6 m) boat with a rotary steam engine coupled to a four-bladed propeller. The craft achieved a speed of 4 mph (6.4 km/h), but Stevens abandoned propellers due to the inherent danger in using the high-pressure steam engines. His subsequent vessels were paddle-wheeled boats. [15]